1. Field of the Invention
This invention lies in the field of weighing and bagging material. More particularly, it concerns a feature which can be added to a conventional weighing machine to continuously monitor the actual weight of the contents of the container, each time a container is filled, adjusting the set point voltage which is the factor which controls the cut-off of flow of material from the hopper, so that by trial and error the amount of material added after the shut off of the principle flow, the resulting weight will be as close as possible to the target weight.
2. Description of the Prior Art
In the prior art it has been possible in the filling of containers to provide a rapid filling means and shut off means and then after the moving material enters the container to make a final total weight of adding to or subtracting from the material in the container to provide an exact weight equal to the target weight. This type of final weighing and adding or subtracting small amounts of material can provide an accurate filling, but makes for a rather slow operation.
In the interest of speeding up the weighing and bagging operation it is sometimes more economical to provide more than the target weight of material in the container than to take the time to remove part of that material in order to reach a closer balance.
It is also possible to have, in a sense, two sources of particulate material that is to be loaded. One would have a large size opening for rapid filling close to the desired target weight, but less than the target weight, and a second smaller flow, and more easily controlled filling means to slowly bring the total weight up to the target weight.
Here again, additional cost of construction and slowness of operation makes it less satisfactory.
Since in all automatic weighing machines there is a comparison being made continuously between the indicated weight of material in the container and a preset, set point weight so that when the two are equal the flow is stopped. In this invention a further simultaneous measurement of the differential weight between the desired target weight and final container weight and depending on how much the overflow or underflow of material there are automatic means for adjusting the set point control voltage up or down as the case may be to compensate for the over or under nominal flow.